MADISON, Wis — Wisconsin tea party groups largely stayed out of endorsing candidates in the U.S. Senate race before the September primary, but now some in the movement are reconsidering and pushing to get behind the Republican candidate Ron Johnson.

Johnson, an Oshkosh millionaire who burst onto the political stage this spring with fiery speeches at two tea party rallies, has a checkered past with some tea party groups. He fell out of favor with the Rock River Patriots after a vetting session in which several members said they were unimpressed with his knowledge of the Constitution.

Straw polls of other tea party groups in Madison and western Wisconsin show that members overwhelmingly backed his opponent Dave Westlake. Other groups, including one in Racine, showed members supported Johnson although they didn't endorse anyone in the primary. A coalition of more than 70 tea party groups did not endorse anyone but may reconsider that for the Nov. 2 general election race against Democratic incumbent Russ Feingold.

Johnson beat Westlake with 85 percent of the primary vote. Johnson spent more than $4 million of his own money blanketing the airwaves, overpowering Westlake who was running on a shoestring budget. After the election Westlake threw his support behind Johnson.

There has been some pressure from local Republicans for the tea party movement to unify behind Johnson, said Tim Dake, organizer of the Milwaukee-area group the GrandSons of Liberty. But Dake and others in the tea party movement say they don't know enough about Johnson to feel comfortable endorsing him.

Dake said Johnson committed to attending roughly a dozen tea party vetting sessions but then canceled at the last minute."We feel we don't really know him at this point," Dake said. "We would kind of like to see some substance. So far we haven't gotten that. ... We don't feel we have a good grasp of who he is and what he would do."

Johnson's spokeswoman Sara Sendek said he is committed to meeting and talking with voters all over the state, including those in the tea party movement.But some in the tea party still feel uncomfortable with Johnson.

"He turns his back on me when I talk to him," said Annette Olson, organizer of the Uninfringed Liberty Group in western Wisconsin near the Minnesota border. "That is more arrogant than Russ Feingold has ever treated me. Russ has not turned his back on me on a one-on-one conversation."

Westlake said he thinks Johnson can mend any hard feelings with tea party groups in the six weeks before the election.

The Fox Valley Initiative, which has members around the Green Bay area, endorsed in the governor's and local U.S. House race, but not in the Senate. Members felt Johnson and Westlake were too similar, but they're likely to discuss whether to back Johnson in the next week or so, said the group's organizer Jim Steineke.

Steineke said he thinks Johnson is the preferred candidate over Feingold because of his business background and because Feingold, an 18-year incumbent, has been in office too long.

Meg Ellefson, organizer of the Wausau Tea Party in central Wisconsin, said she expects her group to get behind Johnson as well but she also said she wanted to meet him and find out more about him.

"I see a lot of myself in Ron Johnson," Ellefson said. "He's new to politics. I think that he makes sense to the regular, average, everyday person."Ellefson said she thinks tea party groups have a responsibility to endorse candidates.

"We have spent the last year criticizing those politicians who we don't support," she said. "Isn't it about time that we actually speak out in support of those we do?"